The present invention relates to disc drive systems. More specifically, the present invention relates to an apparatus for burnishing asperities or surface irregularities from the surface of a disc.
In data processing systems, magnetic disc drives are often used as storage devices. In such devices, read/write heads located on a slider (or an air bearing) are used to write data on or read data from an adjacently rotating disc. The head is located either above or under the disc and isolated therefrom by a thin film of air. The thickness of the thin film of air depends on the disc""s rotational speed and the shape of the air bearing surface. During drive operations, the fly height of the head continuously changes as the head pitches and rolls with the varying topography of the disc. If the quality of the disc or the read/write head is poor, occasional rubbing or sharp contact may occur between the disc and the head. Such contact may damage the head or the disc, which can cause a loss of valuable data.
To efficiently accommodate changes in disc data storage characteristics (i.e., ever-narrowing recording track widths and increases in linear magnetic recording density), the head fly height (or slider clearance) is progressively being decreased. These decreases in fly height can cause the contact frequency between disc and head to increase. To prevent damage to either the disc or head for such low slider clearance, it has been recognized that the surface of the disc should be very flat and free of bumps. Current constraints for maximum defect height are on the order of 0.5 xcexcin. Future designs, already on the horizon, will require roughness less than 0.5 xcexcin.
One procedure that has been used to flatten disc surfaces is a two step glide/burnish process. Within such a process, a glide head is first flown over the disc surface to detect and record asperities high enough to potentially strike a flying read/write head and cause data errors or head crashes. The glide head typically includes an advanced air bearing (AAB) surface designed to enable a particularly low fly height that is lower than most read/write heads fly during normal conditions.
After the glide step is completed, a burnish sweep is performed to remove recorded asperities. The burnish sweep consists of actually contacting the asperities with burnish pads located on an air bearing surface of a flying burnish head, thereby leveling the hits to a desired specification. The glide and burnish steps can be repeated to insure all asperities have been properly reduced or removed.
Traditionally, the burnish head does not include an AAB surface design, resulting in large variances in fly height. Variations in the burnish step can ultimately lead to a decrease in data yield efficiency. However, a burnish head that includes a complex AAB surface and an inefficient configuration of burnish pads can also lead to yield loss.
Because of the tight fly control required for the glide process and the flight variation typical to the burnish head air bearing surface, the traditional burnish head is not suitable to also be used as a glide head. Thus, the glide/burnish process has relied on a lengthy two head process. Each switch between the glide and burnish steps requires use of a separate head.
The present invention provides a solution to this and other problems and offers advantages over the prior art.
The present invention relates to data storage device manufacturing systems that include a hybrid burnish/glide head with advanced air bearing fly height control rails that address the above-mentioned problems.
In accordance with one aspect of the present invention, a disc burnishing system configured to contact and level irregularities located on a surface of a disc is provided. The system includes a motor to rotate the disc at a desired rate and an armature that carries a burnish slider over the surface of the disc. The slider includes at least one raised air bearing rail disposed on and extending from a bottom surface that faces the disc. At least one burnish pad is disposed on the bottom surface and extends towards the disc. Each burnish pad is spaced apart from each raised air bearing rail. In accordance with one embodiment of the system, a defect detection apparatus is operably disposed relative the burnish slider and is utilized to first detect an irregularity before it is burnished.
In accordance with another aspect of the present invention, a burnishing air bearing slider is provided. The slider includes a slider body having an upper surface and a bottom surface opposed to the upper surface. The bottom surface includes a length, a longitudinal axis, a leading edge and a trailing edge. First and second rails are disposed on and extend from the bottom surface and are substantially symmetrical in their position relative the longitudinal axis. Each rail includes a rail trailing end offset from the trailing edge of the bottom surface and a rail leading end that substantially coincides with the leading edge of the bottom surface. The rails provide an aerodynamic lift to the slider body in response to air flow under the slider. A plurality of burnish pads are attached to the bottom surface and positioned along the length of the bottom surface, proximate the trailing edge thereof. The trailing edge of the bottom surface corresponds to a distal end of the slider and the leading edge corresponds to a proximal end of the slider. Accordingly, the burnish pads are positioned in a plurality of locations that are substantially distal in location relative the rail trailing ends. In accordance with one embodiment, a defect detection apparatus is operably disposed relative the slider and enables detection of disc surface irregularities.
These and various other features, as well as advantages that characterize the present invention, will be apparent upon a reading of the following detailed description and review of the associated drawings.